1. Field of the Invention
The present invention relates to an image record apparatus for recording an image using a cut paper sheet having a standard size.
2. Related Background Art
A conventional image record apparatus which uses a standard-size record medium performs a recording operation as follows.
The record medium is set at a predetermined position, and the set record medium is fed from the set position at a predetermined timing in accordance with a record command. The fed record medium is conveyed to a record position by driving a record medium convey motor. A record medium sensor is arranged in the convey path between the record and set positions, and a record control unit detects an instance when the record medium fed from the set position has reached the position of the record medium sensor, thereby recognizing the leading end of the record medium. Simultaneously with the leading end recognition, the record control unit generates a vertical synchronization signal having a predetermined pulse width and supplies it to an image data output control unit so as to adjust the transfer timing of image data on the first record line of the current page. After the record control unit outputs at least the vertical synchronization signal, it generates a horizontal synchronization signal with a predetermined pulse width and supplies it to the image data output control unit so as to adjust the transfer timing of image data from the start pixel position of each line in correspondence with the convey operation of the record medium. Note that the record medium is conveyed at a predetermined speed at least during an interval from the leading end recognition of the record medium by the record medium sensor until the leading end of a recordable range (normally smaller than the record medium size since margins are assured at the leading and trailing ends of the record medium) of the record medium.
After the image data output control unit receives the vertical synchronization signal (a synchronization signal in units of pages), it starts a timer counter or a pulse counter for the horizontal synchronization signal (a synchronization signal in units of lines). When the value of the counter has reached a predetermined value and the leading end of the recordable range of the record medium has reached the record position, the image data output control means starts transfer of record image data in response to the horizontal synchronization signal, and the record control unit performs a recording operation in accordance with the image data.
Furthermore, the image data output control unit sets a maximum number of recordable lines for each page in correspondence with the sub-scan length of the record medium on which an image is to be recorded, and transfers record image data in response to the horizontal synchronization signal within the range of the maximum number of recordable lines. If image data to be recorded has a number of lines larger than the maximum number of recordable lines, the image data output control unit transfers record image data corresponding to the maximum number of recordable lines, and thereafter, outputs a new page control signal to the record control unit to set a new page. Then, the image data output control unit transfers record image data corresponding to the remaining lines.
When the record control unit receives record image data falling outside the recordable range of the record medium, the recorded image cannot fall within the recordable range if a recording operation is performed without additional processing. For this reason, image data corresponding to a portion falling outside the recordable range is not recorded but is abandoned.
The trailing end of the recordable range is recognized in such a manner that the record control unit starts a timer by detecting an instance when the trailing end of the record medium has passed the position of the record medium sensor, and detecting the timing at which the value of the timer has reached a predetermined value. Thus, a record operation on a portion falling outside the recordable range of the record medium is prevented, and other constituting units of the record apparatus can be prevented from being contaminated due to a record operation performed without any record medium at the record position.
As described above, in the conventional image record apparatus, the record control unit detects the leading and trailing ends of the recordable range for each record medium. If the record control unit receives image data corresponding to a portion falling outside the recordable range, it does not record the data, i.e., discards the data. In addition, when the record control unit discards data, it does not return any message indicating it to the image data output source side.
For this reason, in order to prevent omission of an image, in consideration of a case wherein the convey speed of the record medium varies to be higher than a normal speed or a case wherein the record control unit determines, due to a variation in leading end & trailing end detection precision of the record medium or shrinkage of the record medium, that the record medium is short, the recordable range set by the record control unit side must be set to be at least equal to or larger than a range defined by the maximum number of recordable lines set by the image data output control unit side.
Therefore, in order to prevent image omission in every case, the image data output control unit must set the maximum number of recordable lines to be considerably smaller than the maximum value of the image record apparatus. For this reason, in a normal case, the margin at the trailing end of an image becomes undesirably large.